A projection-type image display device capable of projecting a large favorable projection image even in a short distance has become widespread in recent years. The image display devices such as not only a so-called projector that projects a desired image on a wall surface or a screen but also an image display device that is combined with an indoor lighting instrument to emit light together with the image or others and also a vehicular lighting device capable of projecting various pieces of information including a vehicle travel direction onto a road surface where the vehicle is traveling have been studied.
According to the following Patent Document 1, a projection optical device has been already known, the projection optical device having a projection lens composed of a first optical system including a transmittal refractive element and a second optical system including a reflective refractive element, some of lenses of the first optical system being housed in a lower space whose lower limit is a lower end of the second optical system.
According to the following Patent documents 2 and 3, methods each for manufacturing an aspherical optical element have been already known, the methods being for manufacturing an aspherical surface lens in which a molding die for an aspherical surface lens is manufactured by a so-called etching technique and for manufacturing a glass aspherical surface lens by molding and polishing an aspherical surface through a glass molding process on only an aspherical surface of a spherical glass lens.
According to the following Patent Document 4, a method for machining an aspherical surface lens in which a track of an aspherical surface is shaped by using a cam-type spherical center polisher, a device for the machining method and others have been already known.